First, you must understand the question. what % of 60 is 15, so I would write an equation to express this.
15 = 60x
From there, solve for x, so Divide by 60 on each side. The answer is 1/4, or 25%
I think it’s the last one but I’m not sure. Let me know if you get it right.
Answer:

Step-by-step explanation:
Given

Represent charges with d and time with h
So:
when 
Required
Determine the formula

In other words,

Convert to an equation

Where
k = constant of proportion
Substitute values for Charges and Time

Solve for k


Substitute 15 for k in 


<em>The above formula models the situation</em>
Answer:
1/6
Step-by-step explanation:
We want to find how long it takes for the bacteria to lose half its size. We can do this by taking one point of the bacteria and finding how long it takes to go to half its size. When t=0, 9300 * (1/64)^t = 9300 * 1 = 9300 as anything to the power of 0 is 1. Therefore, we can solve for t when the end result of the bacteria is 9300/2= 4650, making our equation
4650 = 9300 * (1/64)^t
divide both sides by 9300
1/2 = (1/64)^t
First, we can tell that 2^6 = 64*. Because of this, we can say that (1/2)^6 = 1^6/2^6 = 1/64, so (1/64)^(1/6) = 1/2. We know this because
(1/2)^6 = 64
take the 6th root of both sides
(1/2) = (64)^(1/6)
. This means that t=1/6, so the bacterial culture loses 1/2 of its size every 1/6 seconds
* if this is harder to figure out, e.g. 3 and 729, we can plug (log₃729) into a calculator